1. Field of the Invention
The present invention relates to an automatic paper feeder used with a printer or the like.
2. Description of Related Art
As is disclosed in, e.g., Japanese Patent Laid-Open Publication No. 12366/1986, a known paper feeder used with a printer is arranged such that a platen for feeding the paper during printing and an ejection of paper and a paper feed mechanism for automatically feeding the paper to the platen are combined to serve as a driving source. In this type of paper feeder having no dedicated driving source, as is stated in the foregoing Publication, there has hitherto been adopted a structure in which power is transferred from the driving source to the paper feed mechanism by the use of intricate cam and link mechanisms interlocking with forward and reverse rotations of the driving source for rotationally driving the platen. After ejecting the paper, the platen is rotated in a reverse direction, i.e., in a direction opposite to that during the printing operation, thus driving the cam and link mechanisms. The power is transferred from the driving source to the paper feed mechanism. Thereafter, the paper is fed by rotating the platen forwards, and at the same time the power transfer from the driving source to the paper feed mechanism is discontinued.
The platen continues its forward rotation until the printed paper is completely ejected. The platen does not start rotating in the reverse direction until the ejection of the paper has been finished. Since one to two seconds after starting the reverse rotation are utilized for a back feed (the paper is fed back), this short period of time is not employed for change-over of the power transfer to the paper feed mechanism. The cam is initially locked after the platen has reversely rotated a given amount in 1 to 2 seconds, and the link is thereby caused to function, thus effecting change-over to the paper feed mechanism. After the change-over is finished, the platen rotates forwardly, and paper feeding is initiated.
In the prior art paper auto-feeder, the power is transferred to the paper feed mechanism by utilizing the reverse rotations of the platen, and hence the platen is not allowed to rotate in a reverse direction until the printed paper is completely ejected. Thus, there arises a problem in the amount of time required for positioning the next paper sheet to the platen, i.e., feeding the paper, because an ejection time is added to the time wherein the platen rotates in the reverse direction. More specifically, the paper feed interval between the first and second sheets of paper is lengthened, resulting in a waste of time. The use of the complicated cam and link mechanisms also leads to a requirement for a large number of parts. This in turn creates problems by enlarging the size of the device, lessening the manufacturability of the device and increasing the costs of the device.